The present invention relates to an earphone or headphone device configuration.
Earphone or headphone device is a mini speaker device that is configured to be inserted into the ear or worn over the ear, or worn adjacent to or in the vicinity of the ear, and is used for personal listening to an audio source. Earphone or headphone device, in contrast to a loudspeaker device which emits sound into the open space, e.g. room or environment (allowing anyone nearby to listen), is configured to allow a single user to listen to an audio source privately. Earphones or headphones are connected to a signal source (e.g. receiver, stereo amplifier, digital devices, like MP3 Player, phone or other handheld communication device, computer, radio, and portable music player), either directly or using a wireless technology.
The performance of an earphone or headphone device, similarly to that of a loudspeaker, is defined by the quality of its sound output (e.g. signal-to-noise; directionality, frequency response, harmonic distortion, etc.). More specifically, the earphone/headphone performance is evaluated by its ability to faithfully reproduce the wave form of the original source, i.e. a degree of match between the profile (frequency and amplitude profile) of a the earphone's output signal and the original source signal.
One of the common problems of earphones/headphones is associated with backwave distortion effects. The backwave distortions are associated with sound waves including those emerging from a back side of the sound waves source (an electroacoustic transducer or headphone driver), and also reflections/diffractions of sound waves from the inner surfaces of the earphone/headphone acoustic cavity and interactions between these reflected/refracted sound waves with the sound waves directly propagating from the loudspeaker towards the output of the earphone/headphone. Since such forward- and backward-generated sound waves are out of phase with each other, their interaction reduces the magnitude of the output signals (being listened). Further, since these sound waves travel different paths through the acoustic cavity, and accordingly arrive at the output of the cavity (and thus at the ear canal) at slightly different times, this introduces destructive phase and timing effects to the reproduced audio including comb-filtering and distortion resulting in loss of audio definition, separation, and overall deteriorated sound quality.